Traditional controllers were designed for systems that output either discrete or continuous signals. More recent hybrid controllers provide integrated control for discrete and continuous signals. Hybrid controlled systems can enable higher performance, versatility, and autonomy. A specific problem in hybrid controllers is resetting the integrator and first order reset elements (FORE).
The state of a linear controller is reset to zero, or same other known value, whenever some threshold is reached. The Clegg integrator and the FORE are now being revisited within the framework of hybrid controllers to overcome fundamental limitations associated with linear feedback, such as overshoot and settling time bounds.
The following U.S. patents describe dynamic state resetting. U.S. Pat. No. 5,929,700 describe a method for a nonlinear notch filter employing a type of filter state resetting with reduced phase lag compared to a linear notch, which is used as part of a controlled system to improve the bandwidth of systems with resonant modes. U.S. Pat. No. 5,694,077 describes a method for resetting different types of filters such as low pass, high pass, and bandpass filters to reduce their phase lag.